An Introduction to a Biology 



representing pollen parents, and to mate the contents at 

 random, the result of each of the three possible unions, 

 9 >^ 9y 9 >^ V) y ^ y^ being known by previous experiment. 

 And the result of the matings of the various kinds of ofi- 

 spring can be predicted from the knowledge which we have 

 of their gametic constitutions. Thus, for example, in jFg' 

 a yellow resulting from the union yellow X yellow^ will 

 produce only yellow when mated with green ; but a second 

 yellow (indistinguishable by outwardly observable features 

 from the first) produced by the union yellow x green mil 

 produce half yellows and half greens when mated with 

 green ; while a green of what ancestry soever will always 

 produce green when mated with green. 



Ex hypothesi Menddiano it is possible to predict the 

 result of these unions for however many generations 

 the experiment is continued, because in its simple 

 form that Law states that the result, for example, of 

 DR xDR will always be the same whether the mating 

 of hybrids takes place in F^ or F^q. The Mendelian hypo- 

 thesis in this simple form may or may not be right ; and 

 I, for one, think that it is not. But this does not damage 

 my argument. My point is that you can determine the 

 properties of the hybrids in different generations — supposing 

 that they are not the same in all ; and having acquired 

 this knowledge you can then return to the counters and see 

 whether the result of mating your material at random can 

 be described by the Law of Ancestral Inheritance. What 

 I want to make clear is that the knowledge of heredity 

 acquired by the MendeUan is deeper, is nearer the pheno- 

 mena themselves, than is that acquired by the biometrician, 

 and is such that the latter, if he is inclined, can use it as 

 material with which to test the Law of Ancestral Inheritance 

 without the labour of conducting a breeding experiment. 



Having devised my method, therefore, I discovered that 

 it was unnecessary to use it. So I abandoned it, in the case 



^ These colours refer to the gametes. 

 194 



